Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$154.96	10.504%	$171.237	$171.24	$171.25	$171.20
Purchase #2	$114.30	8.574%	$124.1001	$124.10	$124.10	$124.10
Purchase #3	$200.28	13.408%	$227.1335	$227.13	$227.15	$227.10
Purchase #4	$94.72	7.182%	$101.5228	$101.52	$101.50	$101.50
Purchase #5	$100.95	12.155%	$113.2205	$113.22	$113.20	$113.20
Purchase #6	$180.83	10.682%	$200.1463	$200.15	$200.15	$200.10
Purchase #7	$221.83	7.497%	$238.4606	$238.46	$238.45	$238.50
7 purchase totals =	$1,067.87		$1,175.8208	$1,175.82	$1,175.80	$1,175.70